This project is designed to investigate the clinical pharmacology of allopurinol in man, to study the biochemical pharmocology of binding of allopurinol and its metabolites to xanthine oxidase, and to investigate the results of using this drug in patients with malignant tumors having rapid tumor lysis following chemotherapy. Assays for allopurinol and its major metabolite oxipurinol have been developed and are sensitive down to concentrations as low as 5 times 10 minus to the 8th power M. Using these assay techniques, the disposition of allopurinol and rate of elimination in man will be investigated. In addition, competitive binding assay techniques to study the biochemistry of binding of allopurinol and its metabolites to xanthine oxidase will be used in hopes of further understanding the molecular pharmocology of the drug. Finally, the effect of allopurinol on the disposition and formation of various purine degradation products will be studied in patients with malignant disease who have rapid tumor lysis following chemotherapy. Patients with various neoplasms will be studied to determine the frequency of hyperuricemia following chemotherapy, serum levels of allopurinol or oxipurinol needed to prevent uric acid nephropathy secondary to tumor lysis, and to quantitate the urinary excretion of purines such as hypoxanthine and xanthine in patients on allopurinol following tumor lysis. These studies will hopefully be of benefit in: 1) understanding the molecular pharmacology of allopurinol, 2) determining allopurinol dosages in the presence of renal failure, 3) determining if the measurement of purine excretion may be used as a marker for the effectiveness of drug therapy and 4) developing an effective plan for the management of acute tumor lysis to prevent nephropathy from either uric acid or xanthine.